1. Field of Invention
This invention relates to catheters or to electrodes arranged and constructed to be inserted into a body cavity. More specifically, the invention involves a catheter containing a large number of electrodes that can be inserted into a patient""s heart to stimulate map cardiac electrical activity, heart wall position, heart wall motion and tissue viability for purposes of medical diagnosis and treatment of congestive heart failure, Bradycardia or tachyarrhythmias. The catheter may be used for other purposes as well. The invention also includes methods for manufacturing the device.
2. Background Art
Cardiovascular disease is the leading cause of death in the United States, Europe and Japan claiming more lives each year than all other diseases combined. The prevalence of this disease has prompted the development of numerous methods and devices to diagnose and treat various cardiac problems. One such device which aids in the diagnosis and treatment of heart disease is the electrode catheter.
In general, various types of catheters containing electrodes have been used to perform endocardial procedures for treatment and diagnosis of cardiac related problems. Examples of these devices include the stimulation catheter of Berkovits U.S. Pat. No. 3,825,015, the flow directed catheter of Blake et. al. U.S. Pat. No. 3,995,623, the multi-contact plunge electrode of Kline U.S. Pat. No. 4,172,451, the defibrillating catheter of Schulte et al. U.S. Pat. No. 5,545,205, the implantation catheter of Obino et al. U.S. Pat. No. 5,800,498 and the pacing lead delivery catheter of Bonner U.S. Pat. No. 6,055,457.
More specifically, in the diagnosis of cardiac conditions, electrode catheters have been used to map cardiac electrical activity. This mapping procedure is useful for the detection and treatment of conduction abnormalities and heart tissue deficiencies. Some cardiac mapping procedures are described in the article entitled: xe2x80x9cTechniques of Intraoperative Electrophysiologic Mappingxe2x80x9d in the American Journal of Cardiology, by John J. Gallagher, et al. which appeared in Volume 49 pages 221-240 January of 1982.
During a typical mapping procedure, a cardiac map is generated by recording the electric signals from the heart and depicting them spatially as a function of time. In an endocardial procedure, an electrode catheter is inserted into a chamber of the heart to measure signals directly by contact with the inside walls of the chamber. Accordingly, the number and placement of electrodes on or within the catheter is an important design consideration for maximizing effectiveness and efficiency for this internal procedure.
Several prior art electrode catheters have been used to generate cardiac maps. Hess U.S. Pat. No. 4,573,473 teaches a catheter with four electrode contacts on a flat planar surface. Gelinas et al. U.S. Pat. No. 4,522,212 teaches a catheter with three or more separated flexible leg electrodes. Chilson U.S. Pat. No. 4,699,147 and Edwards U.S. Pat. No. 5,471,982 define catheters with flexible electrodes that form a basket when extended. Giba et al. U.S. Pat. No. 5,997,526 discloses a shape memory catheter having electrode plates or bands. Unfortunately, such prior art devices are hard to deploy and complicated to manipulate. These difficulties often result in numerous unsuccessful treatment attempts as well as time consuming procedures.
In view of prior art deficiencies, an objective of the present invention is to design an improved cardiac electrode catheter for mapping cardiac electrical activity, heart wall position, heart wall motion and tissue viability.
It is also an objective to design an electrode catheter that is easily deployed, unobtrusive and highly maneuverable.
It is a further objective to provide a catheter and methods of producing the same having a large number of electrodes.
Additional objectives will be apparent from the following description of the invention.
Consistent with these objectives, a catheter constructed in accordance with this invention comprises a collection of wire leads disposed in a flexible tube. Each wire lead has a terminal end, an insulated portion and a non-insulated coiled electrode. The continuous coiled electrode preferably has at least one but no more than twenty-five turns. To prevent the coils from unraveling, each coiled electrode may be glued or fused together, for example, by a knitting or fusing procedure. Each wire lead in the collection is longitudinally staggered so that any one coiled electrode is close to but does not come in contact with the coiled electrode of any other wire lead. The tube is relatively narrow and has a proximal end and a distal end. The tube encloses the insulated portions of the collection of wire leads. Starting at the distal end of the tube, the coiled electrode of each wire lead protrudes from the tube at predetermined longitudinal positions and coils around the exterior of and is attached to the tube. The ends of the collection of wire leads protrude from the proximal end of the tube and are coupled to a suitable connector for connection to an apparatus which may be used to map the cardiac tissues, to monitor the condition of the heart, to apply appropriate therapy, etc. The electrode catheter has a tip member with flexible tines that is attached to the distal end of the tube by a swivel member. The fully assembled catheter can be shaped into various geometric configurations. In the preferred embodiment the catheter has a spiral form that correlates with the shapes of the internal chambers of the heart.
Several different tube configurations may be used in the catheter. In one embodiment, the tube has a longitudinal slit extending along its length, and is tapered on its distal end. The collection of wire leads is installed into the tube by opening the slit and inserting the collection of wires down the length of the tube so that the tube encompasses the insulated mid portions of the wire leads. Simultaneously, the tapered distal end of the tube is inserted through the coiled ends of the wire leads with the coiled end protruding out of the tube through the longitudinal slit.
In another embodiment, the tube has holes drilled through its exterior surface that are just large enough to accommodate the wire lead. The holes are drilled into the tube at an angle with respect to its longitudinal axis and may be in a generally helical pattern around the tube. The insulated portion of a wire lead is inserted into each hole starting with the terminal end. The entire wire lead is moved into the tube until only the coiled end is exposed. The installation of the wire leads may be assisted by pressurized air flow or fluid flow forced down the length of the tube from the distal end. The catheter can also be assembled by using a combination of the above listed methods.
A catheter made in accordance with this invention may also have a separate elongated cavity extending the length of the tubing reserved for a stylet. The stylet is used to implant the lead into the heart in the same manner as a standard pacemaker lead is implanted. The stylet is a solid metal or polymer rod small enough to fit inside the lead.
The stylet is long enough to extend from the insertion point on the proximal end of the lead to the distal tip. When inserted into the lead, the stylet serves to both stiffen and straighten the lead. Because the stylet straightens the lead (from it""s preformed shape) the lead passes more easily through the veins. When the stylet is removed the lead deploys into the selected chamber of the heart.
As it will be clear from the detailed description, the catheter can be used to treat congestive heart failure or a number of conduction abnormalities of the heart such as CHF, Bradycardia, Tachycardia. For example, the catheter can be used to sequentially pace the heart of CHF patients so that a near normal contraction of the muscle takes place. This provides better contraction and increased blood flow.
For patients suffering from Bradycardia, the multi-electrode catheter allows the optimal location(s) within a heart chamber to be paced. Currently, leads are placed in the apex of the right ventricle and pacing from this location has detrimental long term effects on the heart muscle. The catheter of this invention will allow the doctor to select the best pacing site for each patient.
Fast heartbeats (tachyarrhythmias and fibrillations) can be treated with the multielectrode catheter by either preventing or terminating the event. Prevention uses the system""s ability to identify and triangulate the location of a given event and pace the heart in areas that will disrupt the propagation of the arrhythmia. Termination involves delivering low voltage pulses to large areas of the heart, either simultaneously or in rapid sequence. These pulses will have the same effect as a high energy defibrillation pulse in capturing the heart and re-synchronizing the electrical activity of the heart but without the complications of a high energy shock.
Because this catheter is placed in the right side of the heart it allows more consistent and easier lead placement to pace the left ventricle; from the right ventricular outflow tract or the ventricular septum. The lead does not have to be threaded down the great cardiac vein with all of the associated complications and time consuming procedures.